The invention concerns a coil carrier for an electromagnetic actuator, with a winding section for the accommodation of an energisable winding, with an injection moulded plastic body, with a first yoke disc designed as an annular disc and affixed on a first axial face of the winding section, and with an armature guide chamber enclosed by the plastic body for the accommodation of an axially adjustable armature. The invention furthermore concerns an electromagnetic actuator with such a coil carrier.
Coil carriers with a plastic body are of known art, in which is accommodated a metallic armature guide tube for purposes of guiding the armature in its axial adjustment. In such electromagnetic actuators a first yoke disc is positioned on a plane face and affixed during the housing assembly. In this procedure assembly tolerances are problematical. In practice it is only possible with difficulty to install the metallic armature guide tube with a sufficiently small axis misalignment over the tolerance range of all components, as a result of which both mechanical and magnetic disturbing forces can occur in the radial direction, as a result of which increased friction ensues in the mounting, which can lead to premature wear. Moreover a comparatively large radial distance ensues between the adjacent magnetic functional components and the armature, wherein this distance is detrimental to the magnetic force and consequently to the system performance and the efficiency.
In the case of geometrically comparatively large electromagnetic actuators coil carriers are deployed in which the armature is guided not in an armature guide tube, but directly on plastic elevations arranged side-by-side in the peripheral direction and extending in the axial direction. In such electromagnetic actuators the assembly of the first yoke disc takes place by positioning it on a plurality of axial extensions of the plastic body spaced apart from one another in the peripheral direction; these are guided through corresponding passage recesses in the first yoke disc spaced apart from one another in the peripheral direction. The affixing of the yoke disc takes place during the housing assembly. The aforesaid technology has proved itself for the aforementioned, comparatively large actuators with large volume coil carriers, in which the axial extensions have a sufficiently large material strength. The deployment of this technology is problematical in more delicate electromagnetic actuators that operate with comparatively small coil carriers, which do not allow the provision of axial extensions of sufficiently strong material for purposes of positioning the first yoke disc. This can result in various disturbances during assembly and a high scrap rate, since the axial extensions can break during the positioning of the yoke disc. Moreover in the aforesaid technology the radial distance between yoke disc and armature is sometimes still too large and still too afflicted by tolerances; this has a negative effect on the efficiency, which in the case of small magnetic actuators is particularly problematical, since it is not possible to deploy coil windings of any size.
Often in the coil carriers of known art an axial bending up of the plastic walls axially bounding the winding section occurs, since in the prior art winding takes place before the assembly of the yoke disc and the plastic walls axially bounding the winding section have low stability.
From the later published DE 10 2010 055 035 A1 an electromagnetic valve is of known art, in which just one yoke disc is affixed by overmoulding onto the plastic body forming an armature guide chamber.
DE 10 2010 009 400 A1 shows an electromagnetic hydraulic valve in which a multi-part yoke disc is provided, which after the injection moulding process for the manufacture of a plastic body is inserted into corresponding plastic body recesses.
From DE 93 00 039 U1 an electromagnetic actuator is of known art, in which a yoke disc is affixed by means of axial clamping.
From DE 694 17 630 T2 an electromagnetic valve is of known art, which has a tubular metallic core.